Conventionally, axle housings for a drive pinion, a differential assembly, and a pair of axles define a sump into which a volume of lubricant is disposed. The volume of lubricant reduces friction between the drive pinion and a ring gear of the differential assembly, between a pair of side gears and at least a pair of pinion carrier gears, and between components of a plurality of bearings disposed in the axle housing. In addition to reducing friction, the volume of lubricant also disperses heat generated between the moving parts. Depending on a temperature of the axle housing (which may be influenced by an ambient environment of the axle housing or an amount of heat generated by the components therein) and an operational condition of the components of the axle housing, an optimal amount of the volume of lubricant needed varies.
For example, the volume of lubricant disposed in the sump may be too large in many instances. During ordinary operation of a vehicle including the drive axle, when torque loads are well below a maximum amount, the volume of lubricant may result in excess windage of the drive pinion, the differential assembly, and the pair of axles. Such windage may also be exaggerated when the ambient environment of the axle housing is greatly reduced, such as in operation in cold weather. Additionally, during operation in cold weather, the volume of lubricant may disperse heat generated between the moving parts at a rate which prevents a viscosity of the volume of lubricant from decreasing, resulting in excess windage.
Simply reducing the volume of lubricant disposed in the sump to reduce windage results in many unintended consequences. During a torque intensive operation of a vehicle including the drive axle, when torque loads are at or near a maximum amount, a reduced volume of lubricant may not adequately reduce the friction generated by the drive pinion, the differential assembly, and the pair of axles. As a result, the components may wear excessively and operate in a noisy or harsh manner. Additionally, during operation of the axle housing using the reduced volume of lubricant, the lubricant may be unable to disperse heat generated between the moving parts at a rate which prevents premature degradation of the lubricant or damage to seals used in the axle housing.
It would be advantageous to develop a lubricant management system for an axle housing that varies an amount of lubricant used in a sump of the axle housing in a simple and cost effective manner.